This disclosure relates to armatures, and more particularly to an equipoise armature suitable for many uses.
FIG. 1 illustrates a simple balance beam or lever having symmetrical loading of substantially equal weights at each end of the lever, and the fulcrum at the center position of the beam. If the loading at the ends is different, the fulcrum point is moved to keep the beam in balance, as shown in FIG. 2.
If using these concepts for supporting an item, such as a lamp, it is advantageous to employ a “Z” beam, where a pivot is added mid-portion of the beam at either side of the fulcrum, to allow extension/contraction positioning of the ends of beam(s), as illustrated in FIG. 3, with equal loading at the ends, or FIG. 4, with unequal loading.
FIG. 12 is a schematic representation of the device disclosed in U.S. Pat. No. 3,219,303, which 1) is a “pantograph” configuration (with two perpendicular sides extending into arms, and 2) has its balance point on the parallelogram, as opposed to an interior point “C”. With the balance point on the edge corner of the parallelogram, it creates an imbalance when the device out of level. In level position, the balance point “C” is centered over the fulcrum centerline. But, as the device is rotated out of level (down and around) this results in more and more of the device being “all on one side” of the fulcrum centerline: lopsided (see: “A” Device Rotated). The device here will continue to rotate (B) and invert into an upside down hanging equilibrium. Indeed, the built device based on this patent requires a friction screw at the balance point to provide resistance to this overturning tendency. Extending perpendicular parallelogram sides for arms, instead of opposing sides, further exacerbates this lopsidedness.
FIGS. 14 and 15 are diagrams based on the disclosure of U.S. Pat. No. 6,991,199, which is based on a “bent parallelogram” with what looks to be a bridge segment subdividing the parallelogram. On inspection it is observed that the bridge segment “A” is fixed on the table base, and is not free to rotate. Nor is it weight counterbalanced, but spring balanced. FIG. 14 shows the device in a stowed position and FIG. 15 adds the configuration in the extended position. This device is a two position device (stowed, extended), instead of an infinite position device. Its lower portions are bent to create a mechanical advantage for its two positions. These limitations (fixed bridge element; two position limit; and spring counterbalance) are part of what makes this device less desirable.
Whereas the U.S. Pat. No. 6,991,199 patent document represents the “bent parallelogram” as elemental, we observe that one of the corners of the parallelogram below the bridge can be removed and not affect the levering of the parallelogram by the lever arm below the bridge element “A”: the remaining arm with spring counterbalance connection will still lever the device from stowed to extended. What looks to be an important integral part of the parallelogram is, in fact, redundant. This redundancy is part of what makes this device less desirable.
What would be desirable would be to have an armature that allows an object, such as a lamp, magnifier, display, or the like to be re-positionably supported in an efficient manner, remaining balanced whether at a horizontal angle, a vertical angle, in an open position, or in a closed position.